Co-cation conduction of the (Na1-x K x )3.8M0.1P2O7 (M = Ca, Sr, Cd) solid solutions

Samples of systems (Na _1-x K _x )_3.8M_0.1P₂O₇ (M = Ca, Sr, Cd; 0 ≤x ≤ 1) are synthesized. It is established that solid solutions with the structure of γ-K₄P₂O₇ form in these systems. At room temperature, the solutions exist atx ≥ 0.7. In the calcium-containing system, they form a continuous series at temperatures exceeding ∼500°C. The co-cation character of conduction of the solutions is confirmed by measured transport numbers. The concentration dependences of the electroconductivity and its activation energy point to a polyalkali effect, which decreases with an increase in the M²⁺ ion radius. Partial conductivities of sodium and potassium cations in the (Na _1-x K _x )_3.8Ca_0.1P₂O₇ system are calculated and their dependences on the balance between alkali cations in the solid solution are discussed     

Interaction between microwave oscillation and a photoionized semiconductor plasma in a two-layer waveguide

Theoretical studies are performed on the interaction between microwave electromagnetic radiation and a photoionized semiconductor plasma in a two-layer waveguide. The interaction between the characteristic wave types of oscillation and a photoexcited semiconductor plasma is investigated. The dependences of the reflection coefficient and phase of the microwave-frequency wave on the optical radiation intensity are obtained; the effect of the surface and of the geometric dimensions of semiconductor elements on these parameters is investigated.     

The effect of domain wall motion on the nondiagonal impedance component in amorphous wires with circular magnetic anisotropy

The effect of the domain wall motion on the nondiagonal impedance component in amorphous ferromagnetic wires with circular anisotropy was theoretically studied. The frequency spectrum of the electromotive force (emf) induced in the pick-up coil wound around the wire is analyzed. For sufficiently small amplitudes of the ac current passing in the wire, the emf frequency equals doubled frequency of the current. For the ac current amplitudes exceeding certain threshold value, all even harmonics appear in the frequency spectrum of the signal. The emf strongly depends on the longitudinal component of the applied magnetic field at any value of the ac current amplitude. These results can be important for developing frequency transducers controlled by magnetic field.     

Stochastic heating of plasma at electron cyclotron resonance

It is shown theoretically and experimentally that stochastic heating of plasma electrons is highly efficient. Calculations have shown that over the course of 100 periods of an external microwave field the kinetic energy of the particles reaches values of around 1.0 MeV and the average energy reaches values of the order of 0.3 MeV in the field of two oppositely propagating characteristic (eigen) waves of a cylindrical waveguide, with amplitudes 24 kV/cm in a 1 kG stationary magnetic field. Stochastic instability develops as a result of overlapping of non-linear cyclotron resonances. The experimental results agree with the theory: When these waves are excited by a 0.9 MW external source, above a threshold of 0.45 MW one obtains x rays with a photon energy corresponding to a maximum electron energy of the order of 1 MeV over about 800 periods of the external microwave field. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 11, 806–811 (10 June 1999)     

Mechanisms of Interaction of Molybdenum and Tungsten Polyoxide with Aluminum Oxide Melt under Reducing Conditions

The main chemical reactions between Mo and W polyoxides and Al₂O₃ melt in a controlled Ar + H₂ atmosphere (T = 2400 K, P = 1 bar) during sapphire growth by horizontal directional solidification have been investigated. Under these thermodynamic conditions, the melt and products of its dissociative evaporation may actively react with the tungsten heater and molybdenum thermal screens of the crystallization system. It is shown that the polyoxides formed during evaporation do not directly interact with the melt; this interaction occurs only with participation of reagents exhibiting pronounced reducing properties (Al, H₂, H, WO, Al₂O, AlH, AlH₂, AlH₃). It is established that most of processes occur with participation of aluminum hydrides. A particular role of Mo(W) dioxide–W(Mo) polyoxide functional pairs in the interaction with the melt is determined.